Melting Behavior of Polytetra Hydrofuran/Cholesteryl Palmitate Blends Investigated by Two-Dimensional Infrared Correlation Spectroscopy

The melting behavior and miscibility of the polytetra hydrofuran (PTHF)/cholesteryl palmitate (CP) blends was investigated by Fourier transform infrared (FTIR) spectroscopy and generalized two-dimensional infrared (2D IR) correlation spectroscopy. Temperature-dependent spectral variations during the melting process in the C–H stretching (3100–2600 cm−1), C=O stretching (1800–1600 cm−1), and C–O–C stretching (1330–900 cm−1) bands regions were monitored. In the crystalline state, where the molecules form an ordered structure, the dipole-dipole coupling or intermolecular hydrogen bond interactions between the C=O and CH3 groups take place, which have been evidenced by crystalline band at 1715 cm–1 and it shift toward lower frequency. Data analysis during the heating process indicates that the structural adjustment of the PTHF occurs faster than that of the CP, the former (PTHF) forming an amorphous phase more easily.